我的程序似乎无限运行，我不确定它在哪里无法继续

Question

我一直致力于使用 I/O 在 Haskell 中写入文件，但它只是坐在那里运行，没有最终产品。

main :: IO ()
main = do
  hawkID <- getLine
  let text = "module Operations where\nimport " ++ hawkID ++ "\n\nsample :: (" ++ hawkID ++ "a)\nsample = B\n\
                                                                                        \size :: (" ++ hawkID ++ " a) -> Int\nsize x = 0\n\n\
                                                                                        \depth :: (" ++ hawkID ++ " a) -> Int\ndepth x = 0\n\n\
                                                                                        \dropN :: (" ++ hawkID ++ " a) -> (" ++hawkID ++ " a)\ndropN x = x\n\n\
                                                                                        \countB :: (" ++ hawkID ++ " a) -> Int\ncountB x = 0\n\
                                                                                        \ltoB :: (" ++ hawkID ++ " a) -> (" ++ hawkID ++ " b)\nltoB x = B\n\n\
                                                                                        \toString :: (" ++ hawkID ++ " a) -> String\ntoString x = \"\"\n\n\
                                                                                        \mapHawkid :: (a -> b) -> (" ++ hawkID++ " a) -> (" ++ hawkID ++ " b)\n\n\
                                                                                        \substB :: (" ++ hawkID ++ " a) -> (" ++ hawkID ++" a) -> (" ++ hawkID ++ " a)\n\
                                                                                        \substB x y = B"
  let file =  writeFile "Desktop/hawkID.hs"  text

  return ()

Answer 1

您是否正在输入文本并按 Enter 来满足 getLine 调用？不会有提示。如果您需要提示，我认为您需要（例如）putStr 并且可能需要禁用输出缓冲。

此外，您的 writeFile 调用不会被评估 - 您需要将它放在 do 块的主体中​​，例如：

import System.IO

main :: IO ()
main = do
  hSetBuffering stdout NoBuffering
  putStr "Hawk ID: "
  hawkID <- getLine
  let text = ...
  writeFile "hawkID.hs" text